The present disclosure relates spatial light modulators.
In general, a micro mirror array is a type of spatial light modulator (SLM) that includes an array of cells, each of which includes a micro mirror plate that can be tilted about an axis and, furthermore, circuitry for generating electrostatic forces that tilt the micro mirror plate. In one implementation, for example, a digital mode of operation, there are two positions at which the micro mirror plate can be tilted. In an “on” position or state, the micro mirror plate directs incident light to an assigned pixel of a display device. In an “off” position or state, the micro mirror plate directs incident light away from the display device.
A cell typically includes a first structure and a second structure configured to mechanically stop the cell's micro mirror plate at the “on” position and the “off” position, respectively. These structures are referred to in the present specification as mechanical stops. The SLM generally operates by tilting a selected combination of micro mirrors to project light to form appropriate image pixels in a display image. A display device based on SLM is usually required to refresh image frames at high frequencies typical of video applications. Each instance of image frame refreshing can involve the tilting of all or some of the micro mirrors to new respective orientations. Providing fast response tilt movement by the mirrors is therefore crucial to any functional SLM-based display device. One issue with the mirror response rate is related to the stiction, i.e., the contact-surface adhesion, between the lower surface of the mirror and the mechanical stops, which can cause a delay in the mirror tilt response or prevent a mirror from tilting to a new orientation.